Adhesive compositions, particularly conductive adhesives, are used for a variety of purposes in the fabrication and assembly of semiconductor packages and microelectronic devices. The more prominent uses include bonding of electronic elements such as integrated circuit chips to lead frames or other substrates, and bonding of circuit packages or assemblies to printed wire boards. Adhesives useful for electronic packaging applications typically exhibit properties such as good mechanical strength, curing properties that do not affect the component or the carrier, and thixotropic properties compatible with application to microelectronic and semiconductor components.
Recently, there has been an increased interest in b-stageable adhesives. A b-stageable material is actually a thermosetting material that has a first solid phase followed by a rubbery stage at elevated temperature, followed by yet another solid phase at an even higher temperature. The transition from the rubbery stage to the second solid phase is known as thermosetting. However, prior to that, the material behaves similarly to a thermoplastic material. Thus, such a material would permit low lamination temperatures while providing high thermal stability. In addition, b-stageable adhesives eliminate many of the storage, handling, dispensing, and processing issues that exist when dispensing an adhesive in a flowable form. Accordingly, there is a continuing need for b-stageable adhesives in the electronic packaging industry.